I think diversity of thought can just as easily be created with smaller, individual websites. For example, one person can say something and then I can quote them on my website. Only the process is slower and invites less knee-jerk reacting and commenting that seems to live on our dopamine reactions. A natural speed limit created by a lack of quick-reply mechanisms would probably make everyone more thoughtful, and a friction point to responding wouldn't create crowding effects like mass upvoting/downvoting.

The internet is different I think because of it doesn't have the physical limiations of scale. In real life, a small group can get together, yes it can be a sort of "echo chamber", but they are limited by the size of their group which is usually small.

Not really, because thinking by myself can easily be modified with challenging comments. It's much easier for a person to change their mind or ideas (at least if they're open minded) without a million people egging them on. The danger is when a person becomes hyped on their ideas because of mass support for them.